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BAS/BSCR poster abstract
BAS/BSCR37 Discovery and characterisation of novel peptide agonists and the first antagonist for the cardiovascular peptides, the apelins
  1. S L Pitkin1,
  2. N J M Macaluso2,
  3. J J Maguire1,
  4. R C Glen2,
  5. A P Davenport1
  1. 1Clinical Pharmacology Unit, University of Cambridge, Level 6 Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, UK
  2. 2Unilever Centre for Molecular Sciences Informatics, Department of Chemistry, University of Cambridge, Cambridge, UK

Abstract

The recently discovered apelin family of peptides mediate their actions by a single G-protein coupled receptor, APJ. We have previously shown that apelins have three major actions in the human cardiovascular system: endothelium-dependent vasodilatation; direct vasoconstriction by interacting with smooth muscle APJ receptor and increased cardiac contractility by action on cardiac myocytes. Our aim was to discover shorter sequences of (Pyr1)apelin-13 retaining agonist activity and use a computational ligand-based strategy to design cyclic peptide agonists and antagonists. Over 50 compounds were synthesised and tested in a competition binding assay. Functional assays for agonists measured vasoconstrictor action in endothelium-denuded human saphenous veins. Antagonist activity was measured in cyclic AMP assays against (Pyr1)apelin-13. Data are expressed as mean±SE, pD2=−log10EC50, Emax=maximum response. The predicted cleavage product of the angiotensin converting enzyme 2 (ACE-2), apelin-13(1–12), inhibited radiolabelled apelin binding and was identified as the shortest sequence potently constricting endothelium-denuded saphenous vein (pD2 9.07%±0.40, Emax 29.30%±9.43% KCl, n=5). The most potent cyclic analogue identified, MM07, inhibited binding with a KD=86%±30 nM, (n=3) and pD2 10.53%±0.24, Emax 21.80%±5.72% KCl, n=3) with a comparable potency and efficacy to (Pyr1)apelin-13 (pD2=8.8%±0.3, Emax 26%±4%, n=15). MM54 inhibited binding, KD=3.42%±0.45 μmol/l, (n=3) and was identified as an antagonist with a pA2 value of 5.9 in a cyclase inhibition assay. The novel cyclic peptide MM07 retains potency and we have identified the first apelin receptor antagonist, MM54 as a pharmacological tool to characterise the apelin system and in the design of small molecule drugs.

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